Welcome to the world of flowers. You did not say if begonia was "houseplant" type or a fibrous begonia for outdoors. In any case the following should help. Keep evenly moist. Feed biweekly, but withhold from tuberous types during dormant season. Tuberous type - withhold water and store nearly dry at approx. 50degrees F. until time to replant. Any fibrous rooted begonia (except rhizomatous types) can be cut back freely following a period of heavy bloom. Can go outside, also tuberous, but morning sun only & light shade rest of day. Repot once a year in good potting soil. Lift tubers and bring indoors - die if frozen.